The Blue View - Latest and Greatest in Batteries Pt. 2

Boat batteries come in two basic types – starter batteries and house batteries. Starter batteries are designed to provide very large, short term current as the engine is started, then are recharged while the engine is running. These batteries are usually rated by their Cold Cranking Amps (CCA) - a measure of how many amps of current the battery can put out over a 30 second period without discharging the battery. For example, a battery with a CCA rating of 500 amps can provide 500 amps of current over a 30 second period in freezing temperatures and still maintain a voltage of at least 7.2 volts.

House batteries, on the other hand, are used to provide power for all the electrical equipment aboard, from the refrigerator to the laptop computers, and need to be recharged periodically. These batteries are designed to provide a much smaller current over a longer period than are starter batteries, and are rated by the number of amp-hours (ah) they can provide over 20 hours. Thus, a 200 ah battery can provide a constant 10 amps of current over a 20 hour period before becoming fully discharged.

The house batteries on Nine of Cups live most of their lives somewhere between ½ and ¾ full charge. Over the course of a day or two, the electrical demands of the boat slowly discharge them, but before they reach 50% of their full charge, we start the engine for an hour or two to recharge them. This never fully recharges the batteries – it would take several hours to totally top them off – but it does restore them to about 80% of full charge.

Almost every battery manufacturer will tell you this is a bad way to treat their batteries. They should always be recharged to full charge; otherwise the battery life will be much shorter than their normal expected life. Unfortunately, in the real world, this is how cruising sailboat batteries get treated. With our current Lifeline AGM batteries, I partially compensate for this mistreatment by running the engine long enough to fully recharge the battery bank at least once a month. In addition, after the first year or two, I found I needed to equalize the batteries once a quarter. (Equalizing is essentially a very controlled overcharging process that helps remove any sulfation build-up.) In evaluating batteries for a cruising boat, it’s important to consider how mistreating the batteries will affect the battery life, and the cost and time involved in compensating for the abuse they receive.

Since our house batteries are now about 8 years old (that’s about 120 in battery years), I am on a quest to find the best, most cost effective replacement batteries for Cups. So, what are my criteria for the ideal battery? Here is what I think is important – not necessarily in order of importance:

• Long life. Most battery manufacturers provide an important spec – how many times the battery can be recharged before it begins to lose its capacity. Usually, this is a function of how deeply discharged the battery is between recharges. A battery may be rated for 300 recharge cycles if it is always allowed to discharge to 25% of full capacity (Depth of Discharge or DOD) or 450 cycles if it is routinely recharged at 50% DOD (which is why we never let our house batteries discharge below 50% DOD). The more recharge cycles a battery is rated for, the longer its life will be. Depending on the battery type, the number of recharge cycles ranges from 100-200 cycles for an inexpensive battery to well over 4000 cycles for an expensive Li-Ion battery.
• High charging rate. The higher the charging rate, the faster a battery can be recharged and the fewer hours I’ll need to run the engine. This assumes, of course, that the charger – whether it is an alternator or a battery charger – can provide sufficient amps to take advantage of a high charge rate. An 800 amp-hour battery bank being charged by a 100 amp alternator won’t charge all that fast no matter what the maximum charge rate of the battery.
• Low actual cost. Obviously, the less they cost the better, but the true cost of a battery bank is much more than the initial purchase price. What does it cost to maintain them? How about the cost to keep them charged? What is the expected life? A battery that costs $250, but only lasts 2 years is more expensive over its life than a battery that costs $400, but lasts 6 years. There’s also the cost in time, effort and dollars, to swap out those four, 150 pound batteries, and recycle them – you can’t just toss them in the dumpster.
• Low maintenance. How much time is required to keep them maintained and to compensate for my mistreatment of them? Do I need to check acid levels every few weeks? Equalize them once a month?
• High level of safety. All batteries present safety issues. Wet cell lead acid batteries will boil off explosive hydrogen gas if overcharged and can spill acid if tipped over – both of which are possibilities on a sailboat. Sealed Gel and AGM batteries can generate hydrogen gas or can catch fire and burn if overcharged or charged at too high a rate. And we’ve all heard about the fire hazards lithium batteries pose if recharged incorrectly or are ruptured. All batteries present a risk of burns or fire if the terminals are shorted. So, in my mind, while there is no totally risk free battery, the ideal battery would be one that presents the least danger to the boat and crew.

There are a couple of additional things to consider before deciding on which batteries to buy. The first consideration is how many batteries are needed and how large they need to be. The process for determining this is to evaluate our electrical consumption over a 24-hour period. I’ll devote a future blog to this topic, but for now, we’ll assume our daily power usage averages 180 amp-hours. A good rule of thumb is to have a minimum of 3-4 times the daily electrical consumption in battery capacity, so we need batteries with a total capacity of at least 540 to 740 amp-hours.

Another very important consideration is how the boat is used. A sailboat that is used seasonally, maybe taken out for a couple of weeks during the summer and a dozen weekends throughout the year has much different requirements than a full-time cruising boat that spends very little time with shore power. In the first case, the batteries only see 10-20 recharge cycles every year, and even the least expensive batteries will last many years. In the latter case, the batteries may see 200-300 recharge cycles each year, and the less expensive batteries will likely only last a year or two. Thus, the ideal battery for one boat may not be the ideal battery for every boat.

So, let’s make some assumptions and estimates regarding our batteries to help in the selection process.

• Daily Power Consumption. We calculated our average daily power consumption to be around 180 amps. Some days will be considerably more (when we’re passagemaking and running nav instruments and the autopilot, for example), and some days less (when we’re ashore most of the day and not spending hours on the computers, writing blogs).
• Capacity. Most battery types will have a much longer life if we never let them get below 50% DOD. Therefore, we need at least 600 ah of battery capacity. If we are at anchor and want to do some inland travel for a couple of days, it would be nice to have enough reserve capacity to ensure the refrigerator will keep running while we’re gone, so let’s assume we would like at least 800 ah of capacity.

• Recharging. We have solar panels and a wind generator, which combined, average about 80 ah each day, and a shaft generator that puts out quite a bit of power – typically another 60 ah a day when we’re sailing. So, let’s assume we have to replenish around 100 ah per day using the engine. We have a 200 amp alternator, but unless we are running the engine at max rpm, it generates far less amperage than this. We typically run the engine at about 1500 rpm while recharging, which produces around 110 amps. Our engine consumes about 1.4 gallons of fuel per hour at this speed. Fuel prices around the world vary – ranging from $0.12 a gallon in Venezuela to more than $12 a gallon in St. Helena. In the U.S., let’s use an average of $2.50 a gallon for marine diesel, so it costs about $3.50 per hour to recharge at 110 amps per hour.
• Recharge cycles. We are sailing or on the hook about 75% of the time and are without shore power around 275 days each year. We don’t typically need to run the engine every day, so let’s assume we recharge the batteries from 50% DOD 200 days each year.

After all that preliminary stuff, it’s finally time to look at the battery choices. What I plan to do is to examine each type of battery chemistry, list the pros and cons of each, then evaluate the size, weight, number of batteries, purchase price and actual cost of each for our new battery battery bank.

Unfortunately, I’m going to have to put that off until next week’s Blue View – I’m still collecting data and specs from a few battery manufacturers. Stay tuned.

By the way, thanks to the several folks who commented or contacted me regarding battery information and ideas.

The Blue View - Latest & Greatest Batteries

Nine of Cups has two battery banks: a single 8D starter battery, and a four battery, 800 amp-hour bank that supplies power to the ‘house’ – our electronics, lights, pumps, refrigerator/freezer, water desalinator, autopilot, etc. – pretty much everything electrical except the starter. If we are anchored somewhere and are running the refrigerator and using our computers, our solar panels and wind generator usually won’t quite keep up with our daily electrical consumption. Depending on how sunny and/or windy it is, the fully charged house battery bank will typically last 2-4 days, at which time we have to start the engine and recharge the batteries. Batteries can only be recharged a finite number of times before they start losing their capacity, however. The number of recharge cycles depends on several factors. Battery chemistry, depth of discharge before recharging, battery maintenance and battery design are the primary factors that determine a battery’s useful life aboard a cruising boat.

We last bought house batteries for Nine of Cups in Pape’ete, Tahiti, about 8 years ago. At the time, we felt Lifeline AGM batteries were the best option available, and we had them shipped from Florida to Pape’ete. We took care to treat them well, and they lasted considerably beyond their expected life of 3-4 years. For example, we never let them discharge beyond 50% of full charge, and we equalized them at the first sign of sulfation.

But, alas, even our high quality, well maintained Lifeline batteries aren’t recharging well anymore, and no longer respond to equalizing. I plan to do a capacity test on the batteries when we return to Cups to see just how much life is left, but it’s fairly obvious that they are reaching the end of their useful lives.

Replacing our house batteries is not like replacing a car battery. First, it is a major cash outlay. The least expensive price I found online to replace our four Lifeline 4DL batteries will cost us more than $2200! Then we have the difficult task of wrestling four 124 lb (56 kg) batteries out of the boat, and reversing the process with the new ones.

There is also the question of whether the Lifeline batteries are still the best choice for us. We were quite pleased with the current batteries, but a lot has happened in battery technology over the last eight years. Has one of the newer technologies - PTTL, Li-Ion, etc. – matured enough to be better suited to our needs? Is it now more cost effective to go with a different battery type? What new products are available? Would we be further ahead to buy less expensive batteries with shorter lives?

Before we plunk out a couple grand or more on new batteries, I need to do some research to make sure we make the best decision. I plan to spend the next week or two evaluating options, checking specs and doing price comparisons. If you are interested in batteries, you are more than welcome to come along. And if you know more about batteries than I do (which isn’t setting the bar real high), I welcome your input and comments.

The Blue View - Winterizing Nine of Cups

As we are preparing Nine of Cups for a couple of months by herself, one of the jobs on our pre-departure checklist is to prepare her for freezing temperatures. This will be a first for Cups – and us as well. In her entire life, she has never had to be winterized. She grew up with her first parents in Texas, and never saw a hard freeze. Since she’s been ours, we’ve never left her on her own when there was a chance of freezing. So, we had a lot to learn about how best to protect her.

Not to worry. As with most things today, there is no end to internet sources with tons of information on how to winterize a boat. One of the best sources we found was the Boat US site. Since they are in the boat insurance business, they have a vested interest in helping boaters prevent damage – and claims. I did my research and this is the plan I came up with.

• Hot water tank. I removed the intake fitting from the tank, then opened the drain valve, letting the contents of the hot water tank drain into the bilge. Then I connected the inlet and outlet hoses together.
• Fresh water system. Obviously, this is one of the most likely systems to freeze. The entire fresh water system must be purged, then refilled with a non-toxic antifreeze. We pumped the tanks dry using both the pressure pump and foot pump. Then we poured a gallon of propylene glycol antifreeze into each tank and pumped both dry again. Next, we poured two gallons of antifreeze into the port tank and four gallons into the starboard tank. We used the starboard tank to purge all the lines: we opened the faucet furthest from the tank – the sink in the aft head - and let it run until we saw a steady stream of pink water coming out. This was done with both the hot and cold faucets. Then these were closed and we worked backward toward the tank at each faucet.

• Seacocks and thru-hulls. Nine of Cups has twelve thru-hulls with seacocks located below the water line. Two of these, the cockpit drains, have to be left open so that when it rains, any accumulated rain water can drain out of the cockpit. Every other seacock should be winterized. To do this, I closed each seacock and removed the hose from it. Then I drained the hose and used a turkey baster to draw out any remaining water from the seacock. After checking the hose clamps and replacing any that were corroded, I reattached and secured the hose to the seacock.
• Engine raw water cooling system. Our engine uses fresh water for cooling the engine which already had a fresh charge of normal ethylene glycol antifreeze. This coolant, as well as the engine oil and transmission oil, are cooled using seawater that flows through three heat exchangers. The seawater side of the cooling system must be purged and flushed with antifreeze. I started by removing the raw water intake hose, draining it and following the seacock winterizing procedure above. Then I removed the cap from the raw water strainer. One of us started the engine, then watched the water being pumped from the exhaust while the other poured antifreeze into the raw water strainer. Once the exhaust water turned pink, we continued pumping antifreeze through the system for another 30 seconds, then we shut the engine down and put the cap back on the strainer.
• Watermaker. We have a Katadyne watermaker, and I contacted them directly for their recommended process for winterizing. Following their directions, I disconnected the sea water intake from the seacock (after closing it, of course), then drained it and followed the procedure for winterizing the seacocks as above. I added the appropriate amount of membrane preservative to a gallon of food grade antifreeze. This is a more expensive type of propylene glycol with no alcohol or anti-corrosion additives. The gallon of antifreeze was pumped through the watermaker, then shut down.
• Holding tank. Our holding tank was pumped out, then partially filled with fresh water and pumped out again. Then a gallon of antifreeze was poured into it.
• Heads. The intake hose for each head was removed and drained, and the seacock winterized. Before reattaching the hose, a gallon of antifreeze was pumped through the head. The outlet for the aft head is not connected to a holding tank, so after pumping antifreeze through the head, the outlet hose and seacock for it were winterized.
• Deck wash. The inlet hose was drained and the sea cock winterized. Then the inlet hose was dipped into a bucket of antifreeze and the pump turned on until pink water was seen at the deck wash faucet.
• Speed transducer. The speed transducer was removed and replaced with the blank plug.
• Sea water foot pump. The intake hose was drained and the seacock winterized. The intake hose was immersed in a bucket of antifreeze and the foot pump was operated until the discharge water turned pink.
• Fresh water foot pump. The pump was operated until the water was pink.
• Miscellaneous. The tea kettle was drained. The fridge was turned off, cleaned out and left open. The pressure water system breaker was turned off.

We used a total of 15 gallons of non-toxic propylene glycol antifreeze, and one gallon of food grade antifreeze. West Marine conveniently had their antifreeze on sale, so the cost was quite reasonable –certainly cheaper than the cost of repairing a frozen head. The entire process took the better part of a day, but took considerably less time than I expected.

BTW, the average low temp for the Chesapeake City area in December is only 36 degrees F (2 degrees C), so there is a very good chance all this effort was for nothing. Since we did go to the trouble of winterizing Cups, however, I have no doubt the area will experience unseasonably warm temps this year.

My apologies for the lack of pix in this blog. We had every intention of taking a slew of photos while we winterized Cups, then we were so intent on getting the job done, we totally forgot to take a single shot.